Arc tube mounting for high pressure metal vapor lamps



Dec. 27, 1966 E. NILES 3,294,998

ARC TUBE MOUNTING FOR HIGH PRESSURE METAL VAPOR LAMPS Filed Sept. 29,1964 United States Patent 3,294,998 ARC TUBE MOUNTING FOR HIGH PRESSUREMETAL VAPOR LAMPS Everett Niles, Eastlake, Ohio, assignor to GeneralElectric Company, a corporation of New York Filed Sept. 29, 1964, Ser.No. 400,016 7 Claims. (Cl. 3l325) This invention relates tohigh-intensity electric discharge lamps having an arc tube mounted in avitreous outer envelope or jacket. The invention is more particularlyconcerned with the mounting arrangement or structure for supporting thearc tube within the jacket.

A common form of high intensity lamp is the high pressure mercury vaporlamp which generally comprises a quartz arc tube enclosed within a glassouter jacket fitted with a screw base at one end. The are tube isprovided with thermionic self-heating electrodes at opposite ends andcontains a quantity of mercury along with a starting gas. Other kinds ofhigh intensity lamps may use different gas or vapor fillings within thearc tube. Some arc tubes are of materials other than quartz, forinstance a known high pressure sodium vapor arc tube utilizes an aluminaceramic envelope. The outer envelope may be left clear or may be coatedinternally with a phosphor in order to improve the quality or the totalquantity of light emitted by the lamp.

The principal object of the invention is to provide a new and improvedmounting or support structure for the arc tube within the outer envelopeor jacket which is easy and economical to manufacture and strong andreliable in use.

Another object is to provide a support structure for the arc tube whichallows the glass to be worked where the stem is sealed to the neck ofthe outer envelope.

In accordance with the invention, the outer envelope is provided with areentrant dimple of generally cylindrical configuration at its closed ordomed end opposite the base end, and the arc tube supporting frameengages the dimple by means of aclamping member which completes a looparound it. In a preferred embodiment, the supporting frame is a wireharness which extends from the stem at the base end of the outerenvelope to the dimple at the closed end. Part of the harness forms ahalf loop around the dimple, and the loop is completed by a springy clipwhich is fastened to the harness at one end and provides a resilientclamping engagement between the mount and the dimple. The clip may beprovided with a limit lock at its free end to prevent the mount frombecoming completely disengaged from the dimple under shock or vibration.

For further objects and advantages and a better understanding of theinvention, attention is now directed to the following description andaccompanying drawing illustrating embodiments of the invention. Thefeatures believed to be novel will be more particularly pointed out inthe appended claims.

In the drawing:

FIG. 1 is a side elevation view, partly in section, of a high pressuremercury vapor lamp incorporating the improved arc tube mounting of theinvention.

FIG. 2 is an end sectional view looking up along line 2-2 in FIG. 1 andshowing the engagement of the dimple in the domed end of the outerenvelope by the frame.

FIG. 3 is a view similar to that of FIG. 2 and illustrating a variant inthe attachment between frame and dimple.

Referring to the drawing and more particularly to FIG. 1, there is showna high pressure mercury vapor lamp 1 comprising an outer vitreousenvelope or jacket 2 generally of ovoid or ellipsoidal shape andfabricated of hard or soft glass. The neck 3 of the outer envelope isclosed by a reentrant stem 4 having a press 5 through which extendrelatively stiff inlead Wires 6, 7 connected at their outer ends to thecontacts of the usual screw type base 8, namely the threaded shell 9 andthe insulated center contact 11. At the dome end of the envelope, thereis provided a recess or dimple 12 of generally cylindrical configurationwith straight side walls.

The inner arc tube 14 is made of quartz and has enclosed therein atopposite ends a pair of main discharge supporting electrodes 15, 16 oninleads hermetically sealed through the pinched ends 17 of the arc tubeby conventional ribbon seals 18. Each main electrode comprises a coreportion which may be a prolongation of the inner end of the inlead madeof tungsten and surrounded by a double tungsten wire helix. The turns ofthe helix and the interstices between turns are coated with an emittingmixture of alkaline earth oxides. An auxiliary starting electrode 19 isprovided at the base end of the arc tube adjacent main electrode 15, andconsists merely of the inwardly projecting end of the inlead. Theauxiliary electrode is electrically connected to main electrode 15 atthe opposite end of the arc tube through the usual current limitingresistor 20. The arc tube contains a charge of mercury and an inert gassuch as argon at a pressure below millimeters of mercury.

The illustrated lamp corresponds to a 400 watt size and the frame whichlocates and supports the arc tube within the outer envelope is a singleside rod harness made from a continuous length of metal wire, suitablynickel-iron alloy or nickel-plated iron wire. The harness comprises a'principal vertical portion or side rod 21 which extends longitudinallyparallel to the envelope axis substantially from the stem at the baseend to the dimple at the dome end. A short vertical portion 22complements side rod 21 at the lower end and is joined to it by atransverse portion 23 which is welded at its mid-point to inlead wire 6.A similar short vertical portion 24 complements side rod 21 at the upperend and is joined to it by a transverse portion 25. The arc tube issupported in the harness by clamping the flat pinched ends 17 betweenmetal bands 26, 27 which extend between side rod 21 and thecomplementary end portions 22, 24, respectively. The illustrated singleside rod harness causes minimum obstruction of light. In larger sizes oflamps, for instance 1000 watt lamps, where more support is needed, asimilar frame is used but having two side rods, the second rod beingrealized by extending one of vertical portions 22, 24 to join the other.

The frame is anchored at its upper end to the dimple 12 by means of aresilient clamp. The clamp is formed by shaping transverse wire portion25 to make approximately a half loop 28 as it goes around the dimple.The full loop is completed by a springy metal clip or band 29 which isfastened to one side of half loop 28 at one end and extends to theopposite side of the half loop. As illustrated in FIG. 1, wire half loop28 consists of straightsided segments forming half a hexagon. Metal bandhalf loop 29 is shaped in complementary fashion to complete the hexagonand has its end segments overlapping the end segments of the wire loop.One end segment of the band is welded to vertical harness portion 25aand the loop end segment next to it. The resiliency in the clamp comesfrom the metal band 29 which desirably should be made of a materialwhich will withstand the heat of welding without losing its springiness;a suitable material is Monel metal consisting of an alloy of nickel andcopper but stainless steel may also be used.

By shaping the loop members, namely the Wire halfloop 28 and the metalband half-loop 29 with straight sides in a hexagonal configuration, theloop members engage the dimple at a few points, ordinarily three only,spaced around the circumference. In fabricating the lamp, the mountassembly which includes the wire harness or frame fastened to the stemand the arc tube clamped into the frame, is first completed. Then theassembly is inserted into the outer envelope by sliding it in throughthe neck and forcing clamp 28, 29' onto the dimple 12. The slidingmovement of the clamp on the dimple scrapes phosphor oif the dimple inthe case of a phosphor-coated lamp. By limiting the engagement of theclamp on the dimple to a few. points only, the amount of phosphor whichis dislodged is held to a minimum. In sealing the stem 4 to the neck 3,it is desirable to Work the glass of the joint by pulling and pushingthe stem and mount assembly relative to the envelope 2 in order tostretch and compress the soft glass at the joint; the resiliency of theclamp allows the sliding movement of the clamp on the dimple necessaryfor this.

It is desirable that the clamp engage the dimple positively. In theabsence of positive engagement, the arc tube frame will rattle in theouter envelope and this is undesirable. At the same time, the engagementmust beresilient in order to accommodate dimensional variations in thedimple. The springy metal band 29 assures a positive engagement and canbend out to provide a certain range of tolerance. In order to avoidbending or distorting the wire frame of the mount assembly when the loopclamp is driven home around the dimple, a metal band 29 which isrelatively light at the same time as it is springy, must be used.However, this presents the danger that should the lamp be struck sharplyor subjected to a blow after assembly, springy band 29 may be forcedopen and the loop clamp thereupon become completely disengaged from thedimple. Accordingto a feature of the invention, this result is guardedagainst by means of a limit lock formed by tab 31 at the free end ofmetal band 29. The tab is made by bending back a portion of the terminalhalf segment of the metal band and is so placed that it engages verticalportion 25b of the wire frame should the band be forced open too wide.Upon such engagement, further opening of the band is prevented and thisprovides positive assurance against the loop clamp becoming disengagedcompletely from the dimple.

In FIG. 3 a variant of the loop clamp is illustrated wherein the metalband 29 is welded on the inside of the wire half loop and no locking tabis provided. It is primarily on the larger sizes of lamps that thelocking tab is desirable, and the arrangement of FIG. 3 has been foundsuitable for the smaller sizes of high pressure mercury vapor lamps, ingeneral lamps of less than 400 watts rating.

While the invention has been most useful to date in conjunction withhigh pressure mercury vapor lamps and has been so illustrated anddescribed, the principles are broadly applicable to any type of electricdischarge device involving a dual-envelope construction, The specificembodiment which has been illustrated and described in detail isintended of course as exemplary and the scope an inwardly turned dimpleat the other end, an inner arc tube Within said outer envelope, and a.metal frame supporting said are tube within said outer envelope andincluding a transverse portion at said other end, said frame engagingsaid dimple by means of a clamp comprising a first half loop formed insaid transverse portion and a resilient second half loop formed by aspringy clip fastened to one side of the first half loop and extendingto the opposite side thereof, said clamp being proportioned to achieve apositive engagement of said dimple, and said clip allowing entry of thedimple into the clamp upon axial insertion of the frame into the outerenvelope.

3. A dual envelope electric discharge lamp comprising a vitreous outerenvelope having a base at one end and an inwardly turned dimple at theother end, an inner arc tube within said outer envelope, and a metalframe supporting said arc tube within said outer envelope and includinga transverse portion at said other end, said frame engaging said dimpleby means of a clamp comprising'a first half loop formed in saidtransverse portion and a resilient second half loop formed by a springymetal band fastened to one side of the first half loop and extending tothe opposite side thereof, both said half loops being made up ofstraight-sided segments whereby to engage said dimple at spaced pointsonly.

4. A dual envelope electric discharge lamp comprising a vitreous outerenvelope having a dome end and a stem end with a base attached thereto,said envelope having an inwardly turned dimple in the dome end, an innerarc tube within said outer envelope, and a wire harness supporting saidarc tube within said outer envelope comprising a side rod extendingparallel to the axis of said outer envelope from stem to dome end andincluding a transverse wire portion at the dome end, said harnessengaging said dimple by means of a clamp comprising a first half loopformed in said transverse wire portion and a resilient second half loopformed by a springy metal band fastened to one side of the first halfloop and extending to the opposite side thereof.

.5. A dual envelope electric discharge lamp as defined in claim 4 andincluding a limit lock on said resilient secondhalf .loop comprising atab at the free end of said metal band adapted'to engage said oppositeside of said first'half loop after a given opening movement of said ofthe invention is to be determined by the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A dual envelope electric discharge lamp comprising a vitreous outerenvelope having a base at one end and an inwardly turned dimple at theother end, an inner arc tube within said outer envelope, and a framesupporting said are tube within said outer envelope and including :atransverse portion at said other end, said frame engaging said. dimpleby means of a clamp comprising a first half loop formed in saidtransverse portion and a resilient second half loop formed by a springyclip fastened to one side of the first half loop and extending to theopposite side thereof.

2. A dual envelope electric discharge lamp comprising a vitreous outerenvelope having a base atone end and metal band in order to limit theextent of said movement.

6. A duel envelope electric discharge lamp COIHPIIS. ing avitreous outerenvelope having a stem end and a dome end with a base attached thereto,inleads sealed through said stem, said envelope having an inwardlyturned dimple in the dome end, an inner arc tube within said outerenvelope, and a wire harness supporting said arc tube within said outerenvelope comprising a side rod extending parallel to the axis of saidouter envelope from stem to dome end, complementary parallel-extendingwire portions at both ends, and transverse wire portions joining. the.complementary portions to the side rod, one transverse-wire portionbeing fastened to one inlead, the

other transverse Wire portion having a half loop formed therein, aresilient second half loop formed by a springy in claim 6 and includinga limit lock on said resilient sec-1 0nd half loop comprising a tab atthe free end of said metal band adapted to engage said opposite side ofsaid first half-loop after a given opening movement of said metal bandin order to limit the extent of said move-.

ment.

No references cited.

JAMES W. LAWRENCE, Primary Examiner.

C. R, CAMPBELL, Assistant Examiner.

1. A DUAL ENVELOPE ELECTRIC DISCHARGE LAMP COMPRISING A VITREOUS OUTERENVELOPE HAVING A BASE AT ONE END AND AN INWARDLY TURNED DIMPLE AT THEOTHER END, AN INNER ARC TUBE WITHIN SAID OUTER ENVELOPE, AND A FRAMESUPPORTING SAID ARC TUBE WITHIN SAID OUTER ENVELOPE AND INCLUDING ATRANSVERSE PORTION AT SAID OTHER END, SAID FRAME ENGAGING SAID DIMPLE BYMEANS OF A CLAMP COMPRISING A FIRST